The following discussion of the background of the invention is merely provided to aid the reader in understanding the invention and is not admitted to describe or constitute prior art to the present invention.
The term “sepsis” has been used to describe a variety of clinical conditions related to systemic manifestations of inflammation accompanied by an infection. Because of clinical similarities to inflammatory responses secondary to non-infectious etiologies, identifying sepsis has been a particularly challenging diagnostic problem. Recently, the American College of Chest Physicians and the American Society of Critical Care Medicine (Bone et al., Chest 101: 1644-53, 1992) published definitions for “Systemic Inflammatory Response Syndrome” (or “SIRS”), which refers generally to a severe systemic response to an infectious or non-infectious insult, and for the related syndromes “sepsis,” “severe sepsis,” and “septic shock,” and extending to multiple organ dysfunction syndrome (“MODS”). These definitions, described below, are intended for each of these phrases for the purposes of the present application. For purposes of this invention, each of these represents a progressively more severe SIRS category; that is, sepsis is more severe than SIRS, severe sepsis is more severe than sepsis, septic shock is more severe than severe sepsis, and MODS is more severe than septic shock.
“SIRS” refers to a condition that exhibits two or more of the following:
a temperature >38° C. or <36° C.;
a heart rate of >90 beats per minute (tachycardia);
a respiratory rate of >20 breaths per minute (tachypnea) or a PaCO2<4.3 kPa; and
a white blood cell count >12,000 per mm3, <4,000 per mm3, or >10% immature (band) forms.
“Sepsis” refers to SIRS, further accompanied by a clinically evident or microbiologically confirmed infection. This infection may be bacterial, fungal, parasitic, or viral.
“Severe sepsis” refers to sepsis, further accompanied by organ hypoperfusion made evident by at least one sign of organ dysfunction such as hypoxemia, oliguria, metabolic acidosis, or altered cerebral function.
“Septic shock” refers to severe sepsis, further accompanied by hypotension, made evident by a systolic blood pressure <90 mm Hg, or the requirement for pharmaceutical intervention to maintain blood pressure.
MODS (multiple organ dysfunction syndrome) is the presence of altered organ function in a patient who is acutely ill such that homeostasis cannot be maintained without intervention. Primary MODS is the direct result of a well-defined insult in winch organ dysfunction occurs early and can be directly attributable to the insult itself. Secondary MODS develops as a consequence of a host response and is identified within the context of SIRS.
A systemic inflammatory response leading to a diagnosis of SIRS may be related to both infection and to numerous non-infective etiologies, including burns, pancreatitis, trauma, heat stroke, and neoplasia. While conceptually it may be relatively simple to distinguish between sepsis and non-septic SIRS, no diagnostic tools have been described to unambiguously distinguish these related conditions. See, e.g., Llewelyn and Cohen, Int. Care Med. 27: S10-S32, 2001. For example, because more than 90% of sepsis cases involve bacterial infection, the “gold standard” for confirming infection has been microbial growth from blood, urine, pleural fluid, cerebrospinal fluid, peritoneal fluid, synnovial fluid, sputum, or other tissue specimens. Such culture has been reported, however, to fail to confirm 50% or more of patients exhibiting strong clinical evidence of sepsis. See, e.g., Jaimes et al., Int. Care Med 29: 1368-71, published electronically Jun. 26, 2003.
The physiologic responses leading to the systemic manifestations of inflammation in sepsis remain unclear. Activation of immune cells occurs in response to the LPS endotoxin of gram negative bacteria and exotoxins of gram positive bacteria. This activation leads to a cascade of events mediated by proinflammatory cytokines, adhesion molecules, vasoactive mediators, and reactive oxygen species. Various organs, including the liver, lungs, heart, and kidney are affected directly or indirectly by this cascade. Sepsis is also associated with disseminated intravascular coagulation (“DIC”), mediated presumably by cytokine activation of coagulation. Fluid and electrolyte balance are also affected by increases in capillary perfusion and reduced oxygenation of tissues. Unchecked, the uncontrolled inflammatory response created can lead to ischemia, loss of organ function, and death.
Despite the availability of antibiotics and supportive therapy, sepsis represents a significant cause of morbidity and mortality. A recent study estimated that 751,000 cases of severe sepsis occur in the United States annually, with a mortality rate of from 30-50%. Angus et al., Crit. Care Med. 29: 1303-10, 2001. Recently, an organization of medical care groups referred to as the “Surviving Sepsis Campaign” issued guidelines for managing subjects suffering from severe sepsis and septic shock. Dellinger et al., Crit. Care Med. 32: 858-873, 2004. These guidelines draw from, amongst other sources, the “Early Goal Directed Therapy” therapy regimen developed by Rivers and colleagues. See, e.g. New Engl. J. Med. 345: 1368-77. 2001.
Several laboratory tests have been investigated or proposed for use, in conjunction with a complete clinical examination of a subject, for the diagnosis and prognosis of sepsis. See, e.g., U.S. Pat. Nos. 5,639,617 and 6,303,321; Patent publications US2005/0196817, WO2005/048823, WO2004/046181, WO2004/043236, US2005/0164238; and Charpentier et al., Crit. Care Med. 32: 660-65, 2004; Castillo et al., Int. J. Infect. Dis. 8: 271-74, 2004; Chua and Kang-Hoe, Crit. Care 8: R248-R250, 2004; Witthaut et al., Int. Care Med. 29: 1696-1702, 2003; Jones and Kline, Ann. Int. Med. 42: 714-15, 2003; Maeder et al., Swiss Med. Wkly. 133: 515-18, 2003; Giamarellos-Bourboulis et al., Intensive Care Med. 28: 1351-56, 2002; Harbarth et al., Am. J. Respir. Crit. Care Med. 164: 396-402, 2001; Martin et al., Pediatrics 108: (4) e61 1-6, 2001; and Bossink et al., Chest 113: 1533-41, 1998. The use of CCL23 as a marker in sepsis is disclosed in US 2005/0196817 (where it is called by its alternative name MPIF-1) and in WO07/041,623.